Filamentary Resistive Switching in an SrTiO3/TiO2 Heterostructured Nanotube Array

Abstract

In the current study, the resistive switching phenomenon was measured in an SrTiO3/TiO2 heterostructured nanotube array. A highly aligned TiO2 nanotube array was grown by the anodic oxidation method and an SrTiO3 layer was grown by hydrothermal treatment of the TiO2 nanotubes in an Sr(OH)2 precursor of different molarities varying from 0.25 to 25 mM. The morphology and defect density of the nanotubes were altered significantly due the growth of SrTiO3 on the TiO2 nanotubes. The morphology, structure, crystallinity, defects distribution etc. of the SrTiO3/TiO2 heterostructured nanotube array were extensively characterized in the current study. The line profile measurement by energy dispersive spectroscopy envisaged the gradual decrease of the growth of SrTiO3 from the top to the bottom of the nanotube. The Au/SrTiO3–TiO2 heterostructured nanotube/Ti devices were tested for the resistive switching study and electroforming free filamentary-type switching was observed. The SrTiO3/TiO2 heterostructured nanotube synthesized with the 2.5 mM precursor was considered as the best-performing material, exhibiting an ROFF/RON ratio of ∼12 (read voltage: 0.5 V) with excellent retention (106 s) and endurance characteristics. The overall switching study was carried out at below ±2 V. The resistive switching mechanism was explained with a conducting filament formation/rapture model, which was implemented on an individual nanotube and eventually established the multiple-filament approach. The SrTiO3/TiO2 heterojunction also played a significant role by modulating the transport barrier under SET and RESET operations.